Biomass-derived porous carbon materials for advanced lithium sulfur batteries

Biomass, as the most widely used carbon sources, is the main ingredient in the formation of fossil fuels. Biomass-derived novel carbons(BDNCs) have attracted much attention because of its adjustable physical/chemical properties, environmentally friendliness, and considerable economic value. Nature contributes to the biomass with bizarre microstructures with micropores, mesopores or hierarchical pores.Currently, it has been confirmed that biomass has great potential applications in energy storage devices,especially in lithium-sulfur(Li–S) batteries. In this article, the synthesis and function of BDNCs for Li–S batteries are presented, and the electrochemical effects of structural diversity, porosity and surface heteroatom doping of the carbons in Li-S batteries are discussed. In addition, the economic benefits, new trends and challenges are also proposed for further design excellent BDNCs for Li–S batteries.

Advanced chemical strategies for lithium-sulfur batteries: A review

Lithium-sulfur(Li-S) battery has been considered as one of the most promising rechargeable batteries among various energy storage devices owing to the attractive ultrahigh theoretical capacity and low cost. However, the performance of Li-S batteries is still far from theoretical prediction because of the inherent insulation of sulfur, shuttling of soluble polysulfides, swelling of cathode volume and the formation of lithium dendrites. Significant efforts have been made to trap polysulfides via physical strategies using carbon based materials, but the interactions between polysulfides and carbon are so weak that the device performance is limited. Chemical strategies provide the relatively complemented routes for improving the batteries' electrochemical properties by introducing strong interactions between functional groups and lithium polysulfides. Therefore, this review mainly discusses the recent advances in chemical absorption for improving the performance of Li-S batteries by introducing functional groups(oxygen, nitrogen, and boron, etc.) and chemical additives(metal, polymers, etc.) to the carbon structures, and how these foreign guests immobilize the dissolved polysulfides.

500-mW cm^(-2)underwater Zn-H_(2)O_(2)batteries with ultrafine edge-enriched electrocatalysts

Aqueous metal-H_(2)O_(2)cells are emerging as power batteries because of their large theoretical energy densities and multiple application scenarios,especially in underwater environments.However,the peak power densities are less than 300 mW cm^(-2)for most reported metal-H_(2)O_(2)cells based on Mg/Al or their alloys due to the self-corrosion.Herein,we reported a Zn-H_(2)O_(2)cell with ultrafine bean-pod-like ZnCo/N-doped electrocatalysts that were synthesized via multifunctional single-cell-chain biomass.The electrocatalyst provides abundant active sites on the crinkly interface and offers a shortened pathway for electron/ion transfer due to the desired root-like carbon nanotube(CNT)arrays.Therefore,the optimized electrocatalyst exhibited outstanding oxygen reduction reaction(ORR)activity,with high E_(1/2)(0.90 V)and E_(onset)(1.01 V)values.More importantly,Zn-H_(2)O_(2)batteries achieve a record-breaking peak-power density of 510 mW cm^(-2)and a high specific energy density of 953 Wh kg^(-1).

The strategies of advanced cathode composites for lithium-sulfur batteries

Lithium-sulfur batteries have been widely nominated as one of the most promising next-generation electrochemical storage systems due to its low cost, high capacity and energy density. However, its practical application is still hindered by poor cycling lifetime, low Coulombic efficiency, instability and small scales. In the last decade, the electrochemical performances of the lithium-sulfur batteries have been improved by developing various novel nanoarchitectures as qualified hosts, and enhancing the sulfur loading with effective encapsulating strategies. The review summarizes the major sulfur cooperating strategies of cathodes based on background and latest progress of the lithium-sulfur batteries. The novel cooperating strategies of physical techniques and chemical synthesis techniques are discussed in detail. Based on the rich chemistry of sulfur, we paid more attention to the highlights of sulfur encapsulating strategies. Furthermore, the critical research directions in the coming future are proposed in the conclusion and outlook section.

Large-scale multirole Zn(Ⅱ) programmed synthesis of ultrathin hierarchically porous carbon nanosheets

ZIF-derived carbon structures are considered as desired electrode materials for supercapacitors due to their high surface area,high conductivity, and porous structure. However, the most reported ratio of 2-methylimidazole and Zn(II) is 4:1 to 20:1, which limits commercial applications due to the increasing cost. In this paper, a multirole Zn(II)-assisted method is presented from Zn(II) solution, Zn O, Zn O/ZIF-8 core-shell nanostructure, to 3 D hierarchical micro-meso-macroporous carbon structures with a1:1 ratio of 2-methylimidazole and Zn(II). The hierarchically porous carbon has a high surface area of 1800 m2 g^(-1) due to the synergistic effect of multirole Zn(II). The unique carbon-based half-cell delivers the specific capacitances of 377 and 221 F g^(-1) at the current densities of 1.0 and 50 A g^(-1), respectively. As a 2.5 V symmetrical supercapacitor, the device reveals a high doublelayer capacitance of 24.4 F g^(-1), a power density of 62.5 k W kg^(-1), and more than 85.8% capacitance can be retained over 10000 cycles at 10 A g^(-1). More importantly, the low-cost hierarchically porous carbon could be easily produced on a large scale and almost all chemicals can be reused in the sustainable method.

Recent advances in electrocatalysts for non-aqueous Li-O2 batteries

As one of the next-generation energy-storage devices,Li-O_2 battery has become the main research direction for the academic researchers due to its characteristics of environmental friendship,relatively simple structures,high energy density of 3500Wh/kg and low cost.However,Li-O_2 battery cannot be commercialized on a large scale because of the challenging issues including high-efficient electrocatalysts,membranes,Li-based anode and so on.In this review,we focused on the recent development of electrocatalyst materials as cathodes for the non-aqueous Li-O_2 batteries which are relatively simpler than other Li-O_2 batteries＇ structures.Electrocatalysts were summarized including noble metals,nanocarbon materials,transition metals and their hybrids.We points out that the challenges of preparation high-efficient catalysts not only require high catalytic activity and conductivity,but also have novel nanoarchitectures with large interface and porous volume for LiO_x storage.Furthermore,the further investigation of reaction mechanism and advanced in situ analysis technologies are welcome in the coming work.